Eating More Fish Could Help You Avoid Dementia

Source: Elf-Moondance/Pixabay

Medical review by Daniel Miller, M.D.

Boe loved to sing.

She noticed her memory slipping in her early sixties. Her parents had both had Alzheimer’s, and after some years of fierce fighting in their nursing home room–an increase in aggression can be a sign of the disease–they declined so much that they no longer recognized each other. Boe joked, “At least it’s peaceful now.”

So she knew what was coming.

On summer nights, she liked to hold parties that ended with a small group singing on her deck, overlooking a lake in northern New Jersey. Sometimes her neighbors on their decks would even clap.

By the time she was living in a nursing home, it was hard to know if she had recognized you.

Once, in a sitting room full of residents slumped in their chairs with their eyes down, two visitors began singing, “This land is your land. This land is my land.” Boe, beaming, whispered the words. Music-making is one of the skills that lasts even in people with profound dementia (Devere, 2017). The visitors chose songs everyone in that age group knew. A woman in a chair nearby looked up and smiled. They crooned, “How many roads must a man walk down….” Another resident looked up. The visitors sang their hearts out.

Boe knew the gist of the studies about preventing Alzheimer’s, and she exercised and tried to “eat healthy,” as she said, but she didn’t transform her habits.

Diet Is Key

Boe’s attachment to her diet was too bad because the science is stronger every day: What you eat makes a difference. A study in June drew on data from just over 500 Germans, with an average age of about 70. More than 300 had relatives with Alzheimer’s or were already showing signs of impairment themselves. Those who ate mainly fish, vegetables, whole grains, olive oil, fruits, and nuts–which has become known as the Mediterranean diet–had fewer of the tell-tale amyloid plaques and tau tangles, more brain volume in regions vulnerable to Alzheimer’s disease, and better memory (Ballarini et al., 2021).

“We combined several types of data to understand this protective effect of the diet better,” lead author Tommaso Ballarini of the German Center for Neurodegenerative Diseases told MedPage Today, on the idea that the diet “might act as a brake against Alzheimer’s progression” (George, 2021).

Last year, data from two U.S. trials with more than 6,000 participants found that eating more fish protected the brain. In one data set with more than 3,300 participants, researchers measured cognitive performance at two, five, and ten years. The rate of decline in the last five years was slower among those who ate more fish. Eating more vegetables and nuts and drinking less alcohol also helped (Keenan et al., 2020).

How You Can Protect Yourself From Cognitive Decline

The best diet advice to date: Eat fatty fish, vegetables, whole grains, fruits, and nuts.

Obesity and type 2 diabetes are significant risk factors for Alzheimer’s, so anything you can do to lose weight and manage blood sugar is essential.

There is growing evidence that imbalances in the gut affect the brain, making a case for a healthy diet overall, with plenty of prebiotic fiber–abundant in garlic, onions, leeks, oats, and apples–to feed friendly bacteria.

What About Supplements?

Whole fish like salmon fillets may be the better choice for supporting brain health rather than fish oil.

So far, no strategy for taking probiotic supplements has been shown to affect Alzheimer’s (Kruger, 2021). However, omega-3 supplements have been shown to promote short-chain fatty acids, associated with improving gut health (La Rosa, 2018). Research on how these acids affect amyloid plaques is still at the animal-studies stage, focused on mice (Colombo et al., 2021).

Lab investigations and population studies support the idea that omega-3s are good for your brain as well as the rest of you. But studies of supplements have had mixed results. Last year, a small clinical trial suggested why: Among people with the APOE4 gene that increases Alzheimer’s risk by a factor of at least four, omega-3s in the blood are less likely to reach the brain (Arellanes et al.,2020).

The researchers recruited 33 participants who were not cognitively impaired but had a family history of Alzheimer’s, a sedentary lifestyle, and a diet low in fatty fish; 15 carried an APOE4 gene.

Half of the group was randomly chosen to take more than two grams of the omega-3 fatty acid docosahexaenoic acid (DHA) daily for six months. That’s a high dose; the American Heart Association recommends half that amount, which is about what previous trials have tested.

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The other half of the volunteers took placebos, and everyone also took daily B-complex vitamins, which help the body process omega-3s.

The team took samples of blood and cerebrospinal fluid, which required a spinal tap procedure. (You won’t be surprised to hear that the scientists spent two years looking for volunteers; join me in taking a moment to applaud them.)

A Hard Journey From Blood to Brain?

At the end of six months, when the researchers retook the samples, they found a big difference between blood and the fluid in the brain, with much less of a DHA increase in the brain’s fluid—which helps explain why supplements don’t work as well as we’d like. Also, participants who didn’t have the APOE4 gene had three times more DHA in their brain’s fluid.

The answer may be to increase dosages to get that DHA to the brain. It might also be, as William Sears points out, the synergistic combination of nutrients in whole fish, including selenium, iodine, vitamin B12, and more, has a greater ability to support brain health than DHA or fish oil alone.

The team received funding for a larger trial to test whether high doses of omega-3s can slow cognitive decline in APOE4 carriers (Arellanes et al., 2020). We will be watching for their results.

We understand more about diet and the brain every day. However, the fundamentals don’t really change: Stay away from junk. Eat vegetables. Have compassion for your friends struggling with cognitive decline.

And in case I wasn’t clear, eat fish as part of a Mediterranean diet.

A version of this post appears at Vital Choice.